Light emitting diode devices with bonding and/or ohmic contact-reflective material

ABSTRACT

A metal stack of layers contacting an N-type layer of a light emitting diode (LED) device comprises: an ohmic contact layer electrically contacting the N-type layer and having a work function value that is less than or equal to a work function value of the N-type layer; a reflective layer electrically contacting the ohmic contact layer; a first material barrier layer electrically contacting the reflective layer; a current carrying layer electrically contacting the first material barrier layer; and a second material barrier layer electrically contacting the current carrying layer. LED devices incorporate the metal stack of layer as a bonding material and/or as an ohmic contact-reflective material. Methods of making and using the metal stacks and LED devices are also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.63/240,589, filed Sep. 3, 2021, the entire disclosure of which is herebyincorporated by reference herein.

TECHNICAL FIELD

Embodiments of the disclosure generally relate to light emitting diode(LED) devices and methods of manufacturing the same. More particularly,embodiments are directed to metal stacks and LED devices incorporatingthe same. The metal stacks are in contact with an N-type layer of thedevices. The metal stacks comprise: an ohmic contact layer, a reflectivelayer, a first material barrier layer, a current carrying layer, and asecond material barrier layer.

BACKGROUND

A light emitting diode (LED) is a semiconductor light source that emitsvisible light when current flows through it. LEDs combine a p-typesemiconductor with an n-type semiconductor. LEDs commonly use a III-Vgroup compound semiconductor. A III-V group compound semiconductorprovides stable operation at a higher temperature than devices that useother semiconductors. The III-V group compound is typically formed on asubstrate formed of sapphire aluminum oxide (Al₂O₃) or silicon carbide(SiC).

High-intensity/brightness light emitting devices capable of operationacross the visible spectrum include Group III-V semiconductors,particularly binary, ternary, and quaternary alloys of gallium,aluminum, indium, and nitrogen, also referred to as III-nitridematerials. Typically, Ill-nitride light emitting devices are fabricatedby epitaxially growing a stack of semiconductor layers of differentcompositions and dopant concentrations on a growth substrate such as asapphire, silicon carbide, Ill-nitride, or other suitable substrate bymetal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy(MBE), or other epitaxial techniques. Sapphire is often used as thegrowth substrate due to its wide commercial availability and relativeease of use. The stack grown on the growth substrate typically includesone or more n-type layers doped with, for example, Si, formed over thesubstrate, a light emitting or active region formed over the n-typelayer or layers, and one or more p-type layers doped with, for example,Mg, formed over the active region.

Low work function metals are usually employed to form ohmic contact ton-GaN. Currently, the state-of-the-art ohmic contact materials for n-GaNare aluminum (Al) and titanium (Ti) metals, and low contact resistanceto n-GaN is achieved, attributing to low work function of the Al and Timaterials. Due to its better optical reflectivity and electricalconductivity of Al as compared to Ti, Al is commonly used as n-GaN ohmiccontact metal for high power LED devices. Al optical reflectivity ismuch lower than reflective materials such as silver (Ag) and gold (Au),especially at low optical angle of incident, and light long wavelength.Ag or Au, however, is not a good ohmic contact material to n-GaN, due toits high material work function, resulting extreme high contactresistance to n-GaN.

There is a need in the art to provide metal stacks that are suitable forproviding ohmic contact and reflectivity to N-type layers.

SUMMARY

Provided herein are light emitting diode (LED) devices and methods ofmaking and using the same.

In an aspect, a light emitting diode (LED) device comprises:semiconductor layers including an N-type layer, an active region, and aP-type layer; a metal stack of layers contacting the N-type layer, and adielectric material which insulates the P-type layer and the activeregion from the N-bonding material. The metal stack of layers comprises:an ohmic contact layer electrically contacting the N-type layer andhaving a work function value that is less than or equal to a workfunction value of the N-type layer, a reflective layer electricallycontacting the ohmic contact layer, a first material barrier layerelectrically contacting the reflective layer, a current carrying layerelectrically contacting the first material barrier layer, and a secondmaterial barrier layer electrically contacting the current carryinglayer.

A further aspect is a method of manufacturing a metal stack of a lightemitting diode (LED) device, the method comprising: depositing an ohmiccontact layer electrically contacting an N-type layer of the LED deviceand having a work function value that is less than or equal to a workfunction value of the N-type layer; depositing a reflective layerelectrically contacting the ohmic contact layer; depositing a firstmaterial barrier layer electrically contacting the reflective layer;depositing a current carrying layer electrically contacting the firstmaterial barrier layer; and depositing a second material barrier layerelectrically contacting the current carrying layer.

In another aspect, a light emitting diode (LED) device comprises:semiconductor layers including an N-type layer, an active region, and aP-type layer; an N-bonding material electrically contacting the N-typelayer; a P-bonding material electrically contacting the P-type layer andbeing isolated from the N-bonding material; and a first dielectricmaterial which insulates the P-type layer and the active region from theN-bonding material. The N-bonding material being multilayered andcomprising: an ohmic contact layer electrically contacting the N-typelayer and having a work function value that is less than or equal to awork function value of the N-type layer, a reflective layer electricallycontacting the ohmic contact layer, a first material barrier layerelectrically contacting the reflective layer, a current carrying layerelectrically contacting the first material barrier layer, and a secondmaterial barrier layer electrically contacting the current carryinglayer. In one or more embodiments, the LED device is in the form of achip scale package. In one or more embodiments, the LED device is in theform of a micro-LED monolithic array.

A further aspect is a method of manufacturing a light emitting diode(LED) device, the method comprising: preparing a plurality ofsemiconductor layers including an N-type layer, an active region, and aP-type layer; exposing the N-type layer; preparing a bonding materialcontacting the N-type layer; and depositing a dielectric material whichinsulates the P-type layer and the active region from the N-bondingmaterial. The bonding material is formed by: depositing an ohmic contactlayer electrically contacting the N-type layer and having a workfunction value that is less than or equal to a work function value ofthe N-type layer; depositing a reflective layer electrically contactingthe ohmic contact layer; depositing a first N-bonding material barrierlayer electrically contacting the reflective layer; depositing a currentcarrying layer electrically contacting the first material barrier layer;and depositing a second N-bonding material barrier layer electricallycontacting the current carrying layer.

In an aspect, a light emitting diode (LED) device comprises: a pluralityof mesas, each of the mesas comprising semiconductor layers, thesemiconductor layers including an N-type layer, an active region, and aP-type layer, and each mesa having a top surface and at least one mesasidewall; a plurality of trenches between the mesas defined byrespective mesa sidewalls and each having a bottom surface, each of thetrenches containing an N-ohmic contact-reflective material electricallycontacting the N-type layer of each of the mesas; an N-electrode metalcontained by the N-ohmic contact-reflective material, a dielectricmaterial which insulates the P-type layer and the active region from theN-ohmic contact-reflective material; and a P-electrode metal inelectrical contact with the P-type layer of each of the mesas. TheN-ohmic contact-reflective material is multilayered and comprises: anohmic contact layer electrically contacting the N-type layer and havinga work function value that is less than or equal to a work functionvalue of the N-type layer, a reflective layer electrically contactingthe ohmic contact layer, a first material barrier layer electricallycontacting the reflective layer, a current carrying layer electricallycontacting the first material barrier layer, and a second materialbarrier layer electrically contacting the current carrying layer.

A further aspect is a method of manufacturing a light emitting diode(LED) device, the method comprising: preparing a plurality of mesas andtrenches, each of the mesas comprising semiconductor layers, thesemiconductor layers including an N-type layer, an active region, and aP-type layer, and each mesa having a top surface and at least one mesasidewall, and the trenches defined by respective mesa sidewalls and eachhaving a bottom surface; exposing the N-type layer; preparing an N-ohmiccontact-reflective material electrically contacting the N-type layer ofeach of the mesas; depositing and patterning an N-electrode metalcontained by the N-ohmic contact-reflective material and a P-electrodemetal in electrical contact with the P-type layer of each of the mesas;and depositing and patterning a dielectric material which insulates theP-type layer and the active region from the N-ohmic contact-reflectivematerial. The N-ohmic contact-reflective material being prepared by:depositing an ohmic contact layer electrically contacting the N-typelayer and having a work function value that is less than or equal to awork function value of the N-type layer, depositing a reflective layerelectrically contacting the ohmic contact layer, depositing a firstmaterial barrier layer electrically contacting the reflective layer,depositing a current carrying layer electrically contacting the firstmaterial barrier layer, and depositing a second material barrier layerelectrically contacting the current carrying layer.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments. The embodiments as described herein areillustrated by way of example and not limitation in the figures of theaccompanying drawings in which like references indicate similarelements. The figures herein are not to scale.

FIG. 1 a cross-sectional view of a metal stack of layers according toone or more embodiments;

FIG. 2 illustrates a cross-sectional view of an LED device, inparticular, a chip scale package, according to one or more embodiments;

FIG. 3 illustrates a cross-sectional view of an LED device, inparticular, a monolithic uLED array, according to one or moreembodiments;

FIG. 4 illustrates a cross-sectional view of an LED device, inparticular, an array of uLEDs on a substrate, according to one or moreembodiments;

FIG. 5 is a transmission electron microscope (TEM) micrograph of anexcerpt of an exemplary embodiment made according to methods herein;

FIG. 6 provides an exemplary process flow diagram for manufacture of ametal stack according to one or more embodiments;

FIG. 7 provides an exemplary process flow diagram for manufacture of aLED device according to one or more embodiments;

FIG. 8 schematically illustrates a top view of an exemplary displaydevice according to one or more embodiments; and

FIG. 9 schematically illustrates an exemplary display system comprisingLED devices according to embodiments herein.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the disclosure, it isto be understood that the disclosure is not limited to the details ofconstruction or process steps set forth in the following description.The disclosure is capable of other embodiments and of being practiced orbeing carried out in various ways.

The term “substrate” as used herein according to one or more embodimentsrefers to a structure, intermediate or final, having a surface, orportion of a surface, upon which a process acts. In addition, referenceto a substrate in some embodiments also refers to only a portion of thesubstrate, unless the context clearly indicates otherwise. Further,reference to depositing on a substrate according to some embodimentsincludes depositing on a bare substrate, or on a substrate with one ormore films or features or materials deposited or formed thereon.

In one or more embodiments, the “substrate” means any substrate ormaterial surface formed on a substrate upon which film processing isperformed during a fabrication process. In exemplary embodiments, asubstrate surface on which processing is performed includes materialssuch as silicon, silicon oxide, silicon on insulator (SOI), strainedsilicon, amorphous silicon, doped silicon, carbon doped silicon oxides,germanium, gallium arsenide, glass, sapphire, and any other suitablematerials such as metals, metal nitrides, III-nitrides (e.g., GaN, AlN,InN and alloys), metal alloys, and other conductive materials, dependingon the application. Substrates include, without limitation, lightemitting diode (LED) devices, including uLED devices. Substrates in someembodiments are exposed to a pretreatment process to polish, etch,reduce, oxidize, hydroxylate, anneal, UV cure, e-beam cure and/or bakethe substrate surface. In addition to film processing directly on thesurface of the substrate itself, in some embodiments, any of the filmprocessing steps disclosed are also performed on an underlayer formed onthe substrate, and the term “substrate surface” is intended to includesuch underlayer as the context indicates. Thus for example, where afilm/layer or partial film/layer has been deposited onto a substratesurface, the exposed surface of the newly deposited film/layer becomesthe substrate surface.

The term “wafer” and “substrate” will be used interchangeably in theinstant disclosure. Thus, as used herein, a wafer serves as thesubstrate for the formation of the LED devices described herein.

Reference to a micro-LED (uLED or μLED) means a light emitting diodehaving one or more characteristic dimensions (e.g., height, width,depth, thickness, etc. dimensions) of less than 100 micrometers. In oneor embodiments, one or more dimensions of height, width, depth,thickness have values in a range of 2 to 25 micrometers.

Advantages of the devices herein include an inventive metal stack, whichby inserting a thin to very thin optically transparent ohmic contactlayer, e.g., an n-GaN ohmic contact layer, in between an N-type layer,e.g., n-GaN, and a reflective layer (e.g., an Ag or Au mirror). verygood ohmic contact with n-GaN is achieved, while achieving highreflectivity. Such devices are able to achieve low contact resistance(1% work function (Vf) reduction compared to Al baseline), and muchhigher optical extraction (1.5% light output power (LOP) gain ascompared to an Al baseline).

In one or more embodiments, the metal stacks of layers herein areeffective as an an ohmic contact-reflective material for providing lowresistance and high reflectivity in LED devices.

In one or more embodiments, the metal stacks of layers herein areeffective as a bonding material for adhering one or more LED devices toanother structure, such as substrate, or a circuit board, or abackplane, or the like.

Turning to the figures, FIG. 1 illustrates a cross-sectional view of ametal stack of layers according to one or more embodiments, and FIG. 6provides an exemplary process flow diagram 550 for manufacture of ametal stack. Methods of depositing materials, layers, and thin filmsherein include but are not limited to: sputter deposition, evaporationdeposition, atomic layer deposition (ALD), chemical vapor deposition(CVD), physical vapor deposition (PVD), plasma enhanced atomic layerdeposition (PEALD), plasma enhanced chemical vapor deposition (PECVD),and combinations thereof.

Metal stack of layers 100 comprises an ohmic contact layer 151, which isa layer to be in electrical contact, in particular in one or moreembodiments, in direct contact, with an N-layer of a light emittingdiode (LED) device. At operation 551 of FIG. 6 , the ohmic contact layeris deposited so that it is electrically contacting the N-type layer of aplurality of semiconductor layers. In one or more embodiments, the ohmiccontact layer is in direct contact with the N-type layer. The ohmiccontact layer 151 has a work function value that is less than or equalto a work function value of the N-type layer. For example, an N-typelayer of n-GaN has a work function value of approximately 4.1 eV.Exemplary ohmic contact layers according to one or more embodimentscomprise Al (Vf ˜4.06-4.26 eV), Ti (Vf ˜4.0-4.33), or AZO (Al-doped ZnO)(Vf of ˜3.1-4.5). In one or more embodiments, the ohmic contact layercomprises a thickness in a range of greater than or equal to 5 Å to lessthan or equal to 200 Å, and all values and subranges therebetween. Theohmic contact layer is designed to be thick enough to form ohmic contactwith the N-layer and offer sufficient adhesive force for a reflectivelayer 153 (e.g., Ag or Au), while not being too thick such that it doesnot degrade reflectivity of the reflective layer.

Further, it is expected that the ohmic contact layer (e.g., Ti) willreact with the N-layer (e.g., n-GaN) at mesa during downstream thermalcycle steps at an interface, which forms, e.g., TiNx at n-GaN/Tiinterface, which further reduce contact resistance and improve thetransparency. In FIG. 5 , a transmission electron microscope (TEM)micrograph of an excerpt of an exemplary embodiment made according tomethods herein shows a GaN layer on which a Ti ohmic contact layer isdeposited and an Ag reflective layer is on the Ti layer. Reactionbetween the GaN and Ti at their interface is shown by arrow “I”.

The metal stack of layers 100 also comprises the reflective layer 153electrically contacting the ohmic contact layer 151. At operation 553 ofFIG. 6 , the reflective layer 153 is deposited in direct contact withthe ohmic contact layer 151. In one or more embodiments, the reflectivelayer 153 comprises silver (Ag) or gold (Au). In one or moreembodiments, the reflective layer comprises a thickness of greater thanor equal to 1000 Å. In some embodiments, the ohmic contact layer isadvantageously very thin relative to the reflective layer (e.g., greaterthan or equal to 5 Å to less than or equal to 200 Å). In one or moreembodiments, the ohmic contact layer has a thickness of less than orequal to 20% a thickness of the reflective layer, including less than orequal to 10%, 5%, 1%, or 0.5%, and all values and subrangestherebetween.

The metal stack of layers 100 also comprises a first material barrierlayer 157 electrically contacting the reflective layer 153. At operation557 of FIG. 6 , the first material barrier layer 157 is deposited inelectrical contact with the reflective layer 153. In one or moreembodiments, the first material barrier layer 157 is in direct contactwith the reflective layer 153. In other embodiments, when a firstmaterial migration suppression layer 155 is deposited in accordance withoptional operation 555 of FIG. 6 , the first material barrier layer 157is in indirect contact with the reflective layer 153. The first materialbarrier layer 157 impedes and/or prevents metals of the reflective layer153 from forming an intermetallic species or alloy with metals of acurrent carrying layer 159. In one or more embodiments, the firstmaterial barrier layer 157 comprises: titanium (Ti), chromium (Cr),platinum (Pt), cobalt (Co), palladium (Pd), tungsten (W), orcombinations thereof. In one or more embodiments, the first materialbarrier layer 157 comprises a thickness of greater than or equal to 1000Å.

The metal stack of layers 100 also optionally comprises the firstmaterial migration suppression layer 155. In one or more embodiments,the first material migration suppression layer 155 is in direct contactwith the reflective layer 153 on one surface and the first materialbarrier layer 157 on the other surface. The first material migrationsuppression layer 155 can suppress thermal and electrical migration ofmetals of the reflective layer 153. In one or more embodiments, thefirst material migration suppression layer 155 comprises nickel (Ni) orpalladium (Pd). In one or more embodiments, the first material migrationsuppression layer 155 comprises a thickness of greater than or equal to50 Å to less than or equal to 1000 Å, and all values and subrangestherebetween.

The metal stack of layers 100 comprises the current carrying layer 159electrically contacting the first material barrier layer 157. Atoperation 559 of FIG. 6 , the current carrying layer 159 is deposited onthe first material barrier layer 157. In one or more embodiments, thecurrent carrying layer 159 is in direct contact with the first materialbarrier layer 157. In one or more embodiments, the current carryinglayer 159 comprises copper (Cu), gold (Au), aluminum (Al), orcombinations thereof. In one or more embodiments, the current carryinglayer comprises a thickness of greater than or equal to 5000 Å.

The metal stack of layers 100 comprises a second material barrier layer163 electrically contacting the current carrying layer 159 and cappingthe metal stack of layers 100. At operation 563 of FIG. 6 , the secondmaterial barrier layer 163 is deposited in electrical contact with thecurrent carrying layer 159. In one or more embodiments, the secondmaterial barrier layer 163 is in direct contact with the currentcarrying layer 159. In other embodiments, when a second materialmigration suppression layer 161 is deposited in accordance with optionaloperation 561 of FIG. 6 , the second material barrier layer 163 is inindirect contact with the current carrying layer 159. The secondmaterial barrier layer 163 is a protective layer, which impedes and/orprevents attack of the metal stack by downstream processing steps, i.e.dry etch, wet etch, cleaning etc. In one or more embodiments, the secondmaterial barrier layer 163 comprises: titanium (Ti), chromium (Cr),platinum (Pt), cobalt (Co), palladium (Pd), tungsten (W), orcombinations thereof. In one or more embodiments, the second materialbarrier layer 163 comprises a thickness of greater than or equal to 1000Å.

The metal stack of layers 100 also optionally comprises the secondmaterial migration suppression layer 161. In one or more embodiments,the second material migration suppression layer 161 is in direct contactwith current carrying layer 159 on one surface and the second materialbarrier layer 163 on the other surface. The second material migrationsuppression layer 161 can suppress thermal and electrical migration ofmetals of the current carrying layer 159. In one or more embodiments,the second material migration suppression layer 161 comprises nickel(Ni) or palladium (Pd). In one or more embodiments, the second materialmigration suppression layer 161 comprises a thickness of greater than orequal to 50 Å to less than or equal to 1000 Å, and all values andsubranges therebetween. In one or more embodiments, the second materialbarrier layer 163 alone or in combination with the second materialmigration suppression layer 161 is effective as a capping layer for themetal stack 100 as a whole, to protect against degradation duringdownstream process steps.

FIG. 7 provides an exemplary process flow diagram 500 for manufacture ofa LED device according to one or more general embodiments. At operation510, semiconductor layers including N-type layer, active region, andP-type layer are formed according to methods known in the art. In one ormore embodiments, the semiconductor layers are formed by epitaxial (EPI)growth. The semiconductor layers according to one or more embodimentscomprise epitaxial layers, III-nitride layers, or epitaxial III-nitridelayers. In one or more embodiments, the semiconductor layers comprise aIII-nitride material, and in specific embodiments epitaxial III-nitridematerial. In some embodiments, the III-nitride material comprises one ormore of gallium (Ga), aluminum (Al), and indium (In). Thus, in someembodiments, the semiconductor layers comprises one or more of galliumnitride (GaN), aluminum nitride (AlN), indium nitride (InN), aluminumgallium nitride (AlGaN), indium gallium nitride (InGaN), indium aluminumnitride (InAlN), aluminum indium gallium nitride (AlInGaN) and the like.

In one or more embodiments, semiconductor layers are grown on asubstrate, which may remain or may be removed at later points duringmanufacturing. The substrate may be any substrate known to one of skillin the art. In one or more embodiments, the substrate comprises one ormore of sapphire, silicon carbide, silicon (Si), quartz, magnesium oxide(MgO), zinc oxide (ZnO), spinel, and the like. In one or moreembodiments, the substrate is not patterned prior to the growth of theepitaxial layer(s). Thus, in some embodiments, the substrate is notpatterned and can be considered to be flat or substantially flat. Inother embodiments, the substrate is patterned, e.g. patterned sapphiresubstrate (PSS).

In one or more embodiments, the semiconductor layers comprise a stack ofundoped III-nitride material and doped III-nitride material. TheIII-nitride materials may be doped with one or more of silicon (Si),oxygen (O), boron (B), phosphorus (P), germanium (Ge), manganese (Mn),or magnesium (Mg) depending upon whether p-type or n-type III-nitridematerial is needed. In one or more embodiments, the semiconductor layershave a combined thickness in a range of from about 2 μm to about 10 μm,and all values and subranges therebetween.

In one or more embodiments, the active layer is formed between theN-type layer and the P-type layer. The active layer may comprise anyappropriate materials known to one of skill in the art. In one or moreembodiments, the active layer is comprised of a III-nitride materialmultiple quantum wells (MQW), and a III-nitride electron blocking layer.

At operation 515, dielectric material is deposited. Suitable dielectricmaterials include, but are not limited to, silicon oxide (SiO), siliconnitride (SiN), silicon carbide (SiC), aluminum oxide (AlOx), aluminumnitride (AlN) and combinations thereof. The skilled artisan willrecognize that the use of formulas like SiO, to represent silicon oxide,does not imply any particular stoichiometric relationship between theelements. The formula merely identifies the primary elements of thefilm.

At operation 520, etching or patterning is conducted to expose at leastthe N-type layer. According to one or more embodiments, conventionalmasking, wet etching and/or dry etching processes can be used.

At operation 550, a metal stack, suitable as a bonding layer and/or asan ohmic contact-reflective layer is deposited in contact with at leastthe N-type layer. Operation 550 of forming the metal stack is detailedwith respect to FIG. 6 . At operations 570 and 575, any furtherdeposition of materials and/or further etching is conducted to arrive ata desired device configuration.

At operation 580, any further post-processing is performed. In one ormore embodiments, further processing including formation of apassivation layer around a portion or the entirety of a LED or a uLED orthe device as a whole. In one or more embodiments, the processedstructure retains a substrate, is singulated, and is further processed.In one or more embodiments, the processed structure is flipped andaffixed to a support, for example, a tape support, and the substrate isremoved. Removal of the substrate is in accordance with methods known inthe art including substrate laser liftoff. Upon removal of thesubstrate, singulated LEDs or uLEDs are created.

Further processing can include deposition of a down-converter material,e.g. layers of a phosphor material.

FIG. 2 illustrates a cross-sectional view of an LED device according toone or more embodiments. In the embodiment of FIG. 2 , a chip scalepackage 200 comprises semiconductor layers including an N-type layer 204n, an active region 206, and a P-type layer 204 p. The semiconductorlayers reside on a substrate 202.

An N-bonding material 200 n electrically contacts the N-type layer 204n. The N-bonding material 200 n is multi-layered, analogous to 100exemplified in FIG. 1 , and comprises an ohmic contact layer 151electrically contacting the N-type layer and having a work functionvalue that is less than or equal to a work function value of the N-typelayer; a reflective layer 153 electrically contacting the ohmic contactlayer 151; a material barrier layer 157, e.g., for FIG. 2 , a firstN-bonding material barrier layer, electrically contacting the reflectivelayer; a current carrying layer 159 electrically contacting the materialbarrier layer 157 (e.g., the first N-bonding material barrier layer);and another material barrier layer 161, e.g., for FIG. 2 , a secondN-bonding material barrier layer electrically contacting the currentcarrying layer 159. In this embodiment, the ohmic contact layer 151 isin direct contact with the N-type layer 204 n.

A P-bonding material 200 p electrically contacts the P-type layer 204 pby way of a P-metal layer 212, a guardsheet 214, and a current spreadinglayer 208. The P-bonding material 200 p is isolated from the N-bondingmaterial 200 n by second dielectric layer 216 and third dielectric layer218. In one or more embodiments, the P-bonding material 200 p is thesame as the N-bonding material 200 n.

A first dielectric material 210 insulates the P-type layer 204 p and theactive region 206 from the N-bonding material 200 n. The firstdielectric material 210 of FIG. 2 also isolates the current spreadinglayer 208 on the P-type layer 204 p from the N-type layer 204 n.

The P-metal layer 212 resides on the first dielectric material 210 andin a via opening 207 for direct contact with the current spreading layer208 and for electrical contact with the P-type layer. The guardsheet 214is on the p-metal layer 212.

An N-pad 230 contacts the N-bonding layer 200 n through an n-opening 219in the third dielectric layer 218. The N-pad 230 may be multi-layered,comprising one or more of: a seed layer and various n-electrode metals.

A P-pad 220 contacts the P-bonding layer 200 p through an p-opening 217in the third dielectric layer 218. The P-pad 220 may be multi-layered,comprising one or more of: a seed layer and various p-electrode metals.

FIG. 3 illustrates a cross-sectional view of an LED device according toone or more embodiments. In the embodiment of FIG. 3 , a monolithic dieof micro-light emitting diodes (uLEDs) 300 comprises a plurality ofmesas 350, 351 in the form of an array. Mesas 350 and 351 comprisessemiconductor layers including an N-type layer 304 n, an active region306, and a P-type layer 304 p. In this embodiment, the ohmic contactlayer 151 is in direct contact with the N-type layer 304 n.

A current spreading layer 308 is on the P-type layer 304 p. There is nota substrate in this embodiment. Rather, a first portion 301 of theN-type layer 304 n forms a monolithic body, and a second portion 303 ofthe N-type layer in combination with the active region, and the P-typelayer form a plurality of mesas 350, 351 integral to the monolithicbody. A P-metal layer 312 on the current spreading layer 308 on mesa 350yields an active pixel and light upon application of current, and inconjunction with an anode and a cathode. A P-metal layer is not includedon mesa 351, which yields an inactive area, namely no light, uponapplication of current. The mesas 350, 351 are typically formed byetching a structure of semiconductor layers.

An N-bonding material 300 n electrically contacts the first portion 301of the N-type layer 304 n through an N-opening 319 in a dielectricmaterial 316. The N-bonding material is multi-layered, analogous to FIG.1 , and comprises an ohmic contact layer 151 electrically contacting theN-type layer and having a work function value that is less than or equalto a work function value of the N-type layer; a reflective layer 153electrically contacting the ohmic contact layer 151; a material barrierlayer 157, e.g., for FIG. 3 , a first N-bonding material barrier layer,electrically contacting the reflective layer; a current carrying layer159 electrically contacting the material barrier layer 157 (e.g., thefirst N-bonding material barrier layer); and another material barrierlayer 161, e.g., for FIG. 2 , a second N-bonding material barrier layerelectrically contacting the current carrying layer 159.

A P-bonding material 300 p electrically contacts the P-type layer 304 pthrough a p-opening 317 in the dielectric material 316 by way of aP-metal layer 312 and the current spreading layer 308. The P-bondingmaterial 300 p is isolated from the N-bonding material 300 n byphysically being separate. In one or more embodiments, the P-bondingmaterial 300 p is the same as the N-bonding material 300 n.

The dielectric layer material 316 insulates the P-type layer and theactive region from the N-bonding material. The dielectric material 316of FIG. 3 also isolates the current spreading layer 308 on the P-typelayer 304 p from the N-type layer 304 n.

FIG. 4 illustrates a cross-sectional view of an LED device according toone or more embodiments. In the embodiment of FIG. 4 , an array ofmicro-light emitting diodes (uLEDs) 400 comprises a plurality of mesas450. Mesas 450 each comprise semiconductor layers including an N-typelayer 404 n, an active region 406, and a P-type layer 404 p. The mesas450 are typically formed by etching or patterning a structure ofsemiconductor layers on a substrate such that mesas of the semiconductorlayers remain and trenches each having a bottom defined by exposedsurfaces of the substrate between the mesas are created. In someembodiments, after further construction of the device including fillingthe trenches with layers and/or materials, the substrate may be removed.

With respect to etching, according to one or more embodiments, highlyanisotropic etch methods are used to achieve angles ranging fromvertical (90 degrees) to 80 degrees to even smaller values, and allvalues therebetween. In one or more embodiments, depth of themesa/trench etch will typically not exceed 5 micrometers. In one or moreembodiments, an anisotropic etch is used to form trenches. In one ormore embodiments, the width of the mesa is less than 100 micrometers. Inone or more embodiments, the height of the mesa is less than or equal tothe width of the mesa.

Each mesa has a top surface 453 (usually the top of the P-type layer 404p) and at least one mesa sidewall 455. In one or more embodiments, thesemiconductor layers are on a substrate 402. A plurality of trenchesbetween the mesas 450 defined by respective mesa sidewalls 455 and eachhaving a bottom surface 457, each of the trenches containing an N-ohmiccontact-reflective material 400 n electrically contacting the N-typelayer 400 n of each of the mesas 450. The N-ohmic contact-reflectivematerial 400 n is multi-layered, as exemplified in FIG. 1 , andcomprises an ohmic contact layer 151 electrically contacting the N-typelayer and having a work function value that is less than or equal to awork function value of the N-type layer; a reflective layer 153electrically contacting the ohmic contact layer 151; a material barrierlayer 157 electrically contacting the reflective layer; a currentcarrying layer 159 electrically contacting the material barrier layer157; and another material barrier layer 161 electrically contacting thecurrent carrying layer 159. In this embodiment, the ohmic contact layer151 is in direct contact with the N-type layer 404 n.

On top surfaces 453 of each mesa 450, a current spreading layer 408 ison the P-type layer 404 p. Dielectric materials 409, 410, and 411provide electrical isolations. For example, first dielectric material409 insulates the P-type layer 404 p and the active region 406 from theN-ohmic contact-reflective material 400 n. The first dielectric material409 also isolates the current spreading layer 408 on the P-type layer404 p from the N-type layer 404 n.

A P-ohmic contact-reflective material 400 p electrically contacts theP-type layer 404 p through a via 407 in second dielectric material 410by way of a P-metal layer 412 and the current spreading layer 408. TheP-ohmic contact-reflective material 400 p is isolated from the N-ohmiccontact-reflective material 400 n by the first dielectric material 409and the third dielectric material 411. In one or more embodiments, theP-ohmic contact-reflective material 400 p is the same as the N-ohmiccontact-reflective material 400 n.

The device further comprises electrode metals: N-electrode metal 434contained by the N-ohmic contact-reflective material 400 n, andP-electrode metal 424 contained by the P-ohmic contact-reflectivematerial 400 p.

In one or more embodiments, a passivation layer 440 is provided on thefirst dielectric material 409, and the N-electrode metal 434. Underbumpmetallization 442 is optionally on each P-electrode metal 424, which maybe in the form of a plug.

Display Devices

Some display devices comprise single or singulated LEDs or pixels, whichinclude the bonding and/or ohmic contact-reflective material disclosedherein.

Other display devices comprise arrays and groups of LEDs or pixels,which include the bonding and/or ohmic contact-reflective materialdisclosed herein.

FIG. 8 shows a top plan view of an LED monolithic array 800 comprising aplurality of pixels arranged in a grid of 6×19. Pixels 855 a and 855 bare examples. In this embodiment, a common cathode 840 is connected tothe pixels. Anodes, not shown, present on the underside are includedwith each pixel. In one or more embodiments, the array comprises anarrangement of 2×2 mesas, 4×4 mesas, 20×20 mesas, 50×50 mesas, 100×100mesas, or n1×n2 mesas, where each of n1 and n2 is a number in a range offrom 2 to 1000, and n1 and n2 can be equal or not equal.

In one or more embodiments, arrays of micro-LEDs (μLEDs or uLEDs) areused. Micro-LEDs can support high density pixels having a lateraldimension less than 100 μm by 100 μm. In some embodiments, micro-LEDswith dimensions of about 50 μm in diameter or width and smaller can beused. Such micro-LEDs can be used for the manufacture of color displaysby aligning in close proximity micro-LEDs comprising red, blue and greenwavelengths.

In some embodiments, the light emitting arrays include small numbers ofmicro-LEDs positioned on substrates that are centimeter scale area orgreater. In some embodiments, the light emitting arrays includemicro-LED pixel arrays with hundreds, thousands, or millions of lightemitting LEDs positioned together on centimeter scale area substrates orsmaller. In some embodiments, micro-LEDs can include light emittingdiodes sized between 30 microns and 500 microns. The light emittingarray(s) can be monochromatic, RGB, or other desired chromaticity. Insome embodiments, pixels can be square, rectangular, hexagonal, or havecurved perimeter. Pixels can be of the same size, of differing sizes, orsimilarly sized and grouped to present larger effective pixel size.

In some embodiments, light emitting pixels and circuitry supportinglight emitting arrays are packaged and optionally include a submount orprinted circuit board connected for powering and controlling lightproduction by semiconductor LEDs. In certain embodiments, a printedcircuit board supporting light emitting array includes electrical vias,heat sinks, ground planes, electrical traces, and flip chip or othermounting systems. The submount or printed circuit board may be formed ofany suitable material, such as ceramic, silicon, aluminum, etc. If thesubmount material is conductive, an insulating layer is formed over thesubstrate material, and the metal electrode pattern is formed over theinsulating layer. The submount can act as a mechanical support,providing an electrical interface between electrodes on the lightemitting array and a power supply, and also provide heat sinkfunctionality.

In some embodiments, LED light emitting arrays include optical elementssuch as lenses, metalenses, and/or pre-collimators. Optical elements canalso or alternatively include apertures, filters, a Fresnel lens, aconvex lens, a concave lens, or any other suitable optical element thataffects the projected light from the light emitting array. Additionally,one or more of the optical elements can have one or more coatings,including UV blocking or anti-reflective coatings. In some embodiments,optics can be used to correct or minimize two-or three dimensionaloptical errors including pincushion distortion, barrel distortion,longitudinal chromatic aberration, spherical aberration, chromaticaberration, field curvature, astigmatism, or any other type of opticalerror. In some embodiments, optical elements can be used to magnifyand/or correct images. Advantageously, in some embodiments magnificationof display images allows the light emitting array to be physicallysmaller, of less weight, and require less power than larger displays.Additionally, magnification can increase a field of view of thedisplayed content allowing display presentation equals a user's normalfield of view.

Applications

FIG. 9 schematically illustrates an exemplary display system 900utilizing LEDs disclosed herein. The display system 900 comprises an LEDlight emitting array 902 and display 908 in electrical communicationwith an LED driver 904. The display system 900 also comprises a systemcontroller 906, such as a microprocessor. The controller 906 is coupledto the LED driver 904. The controller 906 may also be coupled to thedisplay 908 and to optional sensor(s) 910, and be powered by powersource 912. In one or more embodiments, user data input is provide tosystem controller 906.

In one or more embodiments, the system is a camera flash systemutilizing uLEDs. In such an embodiment, the LED light emitting array 902is an illumination array and lens system and the display 908 comprises acamera, wherein the LEDs of 902 and the camera of 908 may be controlledby the controller 906 to match their fields of view.

Optionally sensors 910 with control input may include, for example,positional sensors (e.g., a gyroscope and/or accelerometer) and/or othersensors that may be used to determine the position, speed, andorientation of system. The signals from the sensors 910 may be suppliedto the controller 906 to be used to determine the appropriate course ofaction of the controller 906 (e.g., which LEDs are currentlyilluminating a target and which LEDs will be illuminating the target apredetermined amount of time later).

In operation, illumination from some or all of the pixels of the LEDarray in 902 may be adjusted—deactivated, operated at full intensity, oroperated at an intermediate intensity. As noted above, beam focus orsteering of light emitted by the LED array in 902 can be performedelectronically by activating one or more subsets of the pixels, topermit dynamic adjustment of the beam shape without moving optics orchanging the focus of the lens in the lighting apparatus.

LED array systems such as described herein may support various otherbeam steering or other applications that benefit from fine-grainedintensity, spatial, and temporal control of light distribution. Theseapplications may include, but are not limited to, precise spatialpatterning of emitted light from pixel blocks or individual pixels.Depending on the application, emitted light may be spectrally distinct,adaptive over time, and/or environmentally responsive. The lightemitting pixel arrays may provide pre-programmed light distribution invarious intensity, spatial, or temporal patterns. Associated optics maybe distinct at a pixel, pixel block, or device level. An example lightemitting pixel array may include a device having a commonly controlledcentral block of high intensity pixels with an associated common optic,whereas edge pixels may have individual optics. In addition toflashlights, common applications supported by light emitting pixelarrays include video lighting, automotive headlights, architectural andarea illumination, and street lighting.

Other applications of LED devices herein include an augmentedreality/virtual reality (AR/VR) systems, which may utilize uLEDsdisclosed herein. One or more AR/VR systems include: augmented (AR) orvirtual reality (VR) headsets, glasses, or projectors. Such AR/VRsystems includes an LED light emitting array, an LED driver (or lightemitting array controller), a system controller, an AR or VR display, asensor system 810. Control input may be provided to the sensor system,while power and user data input is provided to the system controller. Aswill be understood, in some embodiments modules included in the AR/VRsystem can be compactly arranged in a single structure, or one or moreelements can be separately mounted and connected via wireless or wiredcommunication. For example, the light emitting array, AR or VR display,and sensor system can be mounted on a headset or glasses, with the LEDdriver and/or system controller separately mounted.

In one embodiment, the light emitting array can be used to project lightin graphical or object patterns that can support AR/VR systems. In someembodiments, separate light emitting arrays can be used to providedisplay images, with AR features being provided by a distinct andseparate micro-LED array. In some embodiments, a selected group ofpixels can be used for displaying content to the user while trackingpixels can be used for providing tracking light used in eye tracking.Content display pixels are designed to emit visible light, with at leastsome portion of the visible band (approximately 400 nm to 750 nm). Incontrast, tracking pixels can emit light in visible band or in the IRband (approximately 750 nm to 2,200 nm), or some combination thereof. Asan alternative example, the tracking pixels could operate in the 800 to1000 nanometer range. In some embodiments, the tracking pixels can emittracking light during a time period that content pixels are turned offand are not displaying content to the user.

The AR/VR system can incorporate a wide range of optics in the LED lightemitting array and/or AR/VR display, for example to couple light emittedby the LED light emitting array into AR/VR display as discussed above.For AR/VR applications, these optics may comprise nanofins and bedesigned to polarize the light they transmit.

In one embodiment, the light emitting array controller can be used toprovide power and real time control for the light emitting array. Forexample, the light emitting array controller can be able to implementpixel or group pixel level control of amplitude and duty cycle. In someembodiments, the light emitting array controller further includes aframe buffer for holding generated or processed images that can besupplied to the light emitting array. Other supported modules caninclude digital control interfaces such as Inter-Integrated Circuit(I2C) serial bus, Serial Peripheral Interface (SPI), USB-C, HDMI,Display Port, or other suitable image or control modules that areconfigured to transmit needed image data, control data or instructions.

In operation, pixels in the images can be used to define response ofcorresponding light emitting array, with intensity and spatialmodulation of LED pixels being based on the image(s). To reduce datarate issues, groups of pixels (e.g. 5×5 blocks) can be controlled assingle blocks in some embodiments. In some embodiments, high speed andhigh data rate operation is supported, with pixel values from successiveimages able to be loaded as successive frames in an image sequence at arate between 30 Hz and 100 Hz, with 60 Hz being typical. Pulse widthmodulation can be used to control each pixel to emit light in a patternand with an intensity at least partially dependent on the image.

In some embodiments, the sensor system can include external sensors suchas cameras, depth sensors, or audio sensors that monitor theenvironment, and internal sensors such as accelerometers or two or threeaxis gyroscopes that monitor AR/VR headset position. Other sensors caninclude but are not limited to air pressure, stress sensors, temperaturesensors, or any other suitable sensors needed for local or remoteenvironmental monitoring. In some embodiments, control input can includedetected touch or taps, gestural input, or control based on headset ordisplay position. As another example, based on the one or moremeasurement signals from one or more gyroscope or position sensors thatmeasure translation or rotational movement, an estimated position ofAR/VR system relative to an initial position can be determined.

In some embodiments, the system controller uses data from the sensorsystem to integrate measurement signals received from the accelerometersover time to estimate a velocity vector and integrate the velocityvector over time to determine an estimated position of a reference pointfor the AR/VR system. In other embodiments, the reference point used todescribe the position of the AR/VR system can be based on depth sensor,camera positioning views, or optical field flow.

Based on changes in position, orientation, or movement of the AR/VRsystem, the system controller can send images or instructions the lightemitting array controller. Changes or modification the images orinstructions can also be made by user data input, or automated datainput as needed. User data input can include but is not limited to thatprovided by audio instructions, haptic feedback, eye or pupilpositioning, or connected keyboard, mouse, or game controller.

Embodiments

Various embodiments are listed below. It will be understood that theembodiments listed below may be combined with all aspects and otherembodiments in accordance with the scope of the invention.

Embodiment (a). A light emitting diode (LED) device comprising: aplurality of mesas, each of the mesas comprising semiconductor layers,the semiconductor layers including an N-type layer, an active region,and a P-type layer, and each mesa having a top surface and at least onemesa sidewall; a plurality of trenches between the mesas defined byrespective mesa sidewalls and each having a bottom surface, each of thetrenches containing an N-ohmic contact-reflective material electricallycontacting the N-type layer of each of the mesas, the N-ohmiccontact-reflective material being multi-layered, and comprising: anohmic contact layer electrically contacting the N-type layer and havinga work function value that is less than or equal to a work functionvalue of the N-type layer, a reflective layer electrically contactingthe ohmic contact layer, a first material barrier layer electricallycontacting the reflective layer, a current carrying layer electricallycontacting the first material barrier layer, and a second materialbarrier layer electrically contacting the current carrying layer; anN-electrode metal contained by the N-ohmic contact-reflective material,a dielectric material which insulates the P-type layer and the activeregion from the N-ohmic contact-reflective material; and a P-electrodemetal in electrical contact with the P-type layer of each of the mesas.

Embodiment (b). The LED device of embodiment (a), wherein the N-ohmiccontact-reflective material is in direct contact with the N-type layer.

Embodiment (c). The LED device of any of embodiments (a) to (b), whereinthe N-type layer comprises n-GaN and: the ohmic contact layer comprises:aluminum (Al), titanium (Ti), or aluminum-doped zinc oxide (AZO), thereflective layer comprises silver (Ag) or gold (Au); the first andsecond material barrier layers each independently comprise: titanium(Ti), chromium (Cr), platinum (Pt), cobalt (Co), palladium (Pd), ortungsten (W), and the current carrying layer comprises: copper (Cu),gold (Au), or aluminum (Al).

Embodiment (d). The LED device of any of embodiments (a) to (c),wherein: the ohmic contact layer comprises a thickness in a range ofgreater than or equal to 5 Å to less than or equal to 200 Å, thereflective layer comprises a thickness of greater than or equal to 1000Å, the first and second material barrier layers each independentlycomprise a thickness of greater than or equal to 1000 Å, and the currentcarrying layer comprises a thickness of greater than or equal to 5000 Å.

Embodiment (e). The LED device of any of embodiments (a) to (d), whereinthe N-ohmic contact-reflective material further comprises a firstmaterial migration suppression layer electrically contacting thereflective layer and the first material barrier layer; and a secondmaterial migration suppression layer electrically contacting the currentcarrying layer and the second material barrier layer.

Embodiment (f). The LED device of embodiment (e), wherein the first andsecond material migration suppression layers each independently comprisenickel (Ni) or palladium (Pd), and/or independently comprise a thicknessin a range of greater than or equal to 50 Å to less than or equal to1000 Å.

Embodiment (g). The LED device of any of embodiments (a) to (f) furthercomprising a P-ohmic contact-reflective material containing theP-electrode metal, wherein the P-ohmic contact-reflective material hasthe same structure as the N-ohmic contact-reflective material.

Embodiment (h). The LED device of any of embodiments (a) to (g), whereineach of the mesas has at least one characteristic dimension of less than100 micrometers, the character dimension being selected from the groupconsisting of: height, width, and depth.

Embodiment (i). The LED device of any of embodiments (a) to (h), whereinthe semiconductor layers are epitaxial semiconductor layers having anoverall thickness in a range of from 2 μm to 10 μm.

Embodiment (j). The LED device of any of embodiments (a) to (i), whereineach of the mesas includes sidewalls of the semiconductor layersdefining an angle in a range of from 60 degrees to 90 degrees from ahorizontal plane that is parallel with the N-type layer and the P-typelayer.

Embodiment (k). The LED device of any of embodiments (a) to (j), whereinthe plurality of mesas are integral to a monolithic die.

Embodiment (l). The LED device of any of embodiments (a) to (j), whereinthe semiconductor layers are on a substrate.

Embodiment (m). A method of manufacturing a light emitting diode (LED)device comprising: preparing a plurality of mesas and trenches, each ofthe mesas comprising semiconductor layers, the semiconductor layersincluding an N-type layer, an active region, and a P-type layer, andeach mesa having a top surface and at least one mesa sidewall, and thetrenches defined by respective mesa sidewalls and each having a bottomsurface; exposing the N-type layer; preparing an N-ohmiccontact-reflective material electrically contacting the N-type layer ofeach of the mesas by: depositing an ohmic contact layer electricallycontacting the N-type layer and having a work function value that isless than or equal to a work function value of the N-type layer,depositing a reflective layer electrically contacting the ohmic contactlayer, depositing a first material barrier layer electrically contactingthe reflective layer, depositing a current carrying layer electricallycontacting the first material barrier layer, and depositing a secondmaterial barrier layer electrically contacting the current carryinglayer; depositing and patterning an N-electrode metal contained by theN-ohmic contact-reflective material and a P-electrode metal inelectrical contact with the P-type layer of each of the mesas; anddepositing and patterning a dielectric material which insulates theP-type layer and the active region from the N-ohmic contact-reflectivematerial.

Embodiment (n). The method of embodiment (m) comprising depositing theN-ohmic contact-reflective material directly on the N-type layer.

Embodiment (o). The method of any of embodiments (m) to (n), wherein theN-type layer comprises n-GaN, and the ohmic contact layer comprises:aluminum (Al), titanium (Ti), or aluminum-doped zinc oxide (AZO); thereflective layer comprises silver (Ag) or gold (Au); the first andsecond material barrier layers each independently comprise: titanium(Ti), chromium (Cr), platinum (Pt), cobalt (Co), palladium (Pd), ortungsten (W); and the current carrying layer comprises: copper (Cu),gold (Au), or aluminum (Al).

Embodiment (p). The method of any of embodiments (m) to (o), wherein:the ohmic contact layer comprises a thickness in a range of greater thanor equal to 5 Å to less than or equal to 200 Å, the reflective layercomprises a thickness of greater than or equal to 1000Å,

the first and second material barrier layers each independently comprisea thickness of greater than or equal to 1000 Å, and the current carryinglayer comprises a thickness of greater than or equal to 5000 Å.

Embodiment (q). The method of any of embodiments (m) to (p), furthercomprising: depositing a first material migration suppression layerelectrically contacting the reflective layer and the first materialbarrier layer; and/or a second material migration suppression layerelectrically contacting the current carrying layer and the secondmaterial barrier layer.

Embodiment (r). The method of any of embodiment (q), wherein the firstand second material migration suppression layers each independentlycomprise nickel (Ni) or palladium (Pd), and/or independently comprise athickness in a range of greater than or equal to 50 Å to less than orequal to 1000 Å.

Embodiment (s). The method of any of embodiments (m) to (r), wherein aP-bonding material is also prepared contacting the P-type layer bydepositing the ohmic contact layer electrically contacting the P-typelayer, depositing the reflective layer electrically contacting the ohmiccontact layer, depositing the first N-bonding material barrier layerelectrically contacting the reflective layer, depositing the currentcarrying layer electrically contacting the first material barrier layer.

The method of any of embodiments (m) to (s), wherein each of the mesashas at least one characteristic dimension of less than 100 micrometers,the character dimension being selected from the group consisting of:height, width, and depth.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe disclosure. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the disclosure.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims. It is also understood that other embodiments of this inventionmay be practiced in the absence of an element/step not specificallydisclosed herein.

What is claimed is:
 1. A light emitting diode (LED) device comprising: aplurality of mesas, each of the mesas comprising semiconductor layers,the semiconductor layers including an N-type layer, an active region,and a P-type layer, and each mesa having a top surface and at least onemesa sidewall; a plurality of trenches between the mesas defined byrespective mesa sidewalls and each having a bottom surface, each of thetrenches containing an N-ohmic contact-reflective material electricallycontacting the N-type layer of each of the mesas, the N-ohmiccontact-reflective material being multi-layered, and comprising: anohmic contact layer electrically contacting the N-type layer and havinga work function value that is less than or equal to a work functionvalue of the N-type layer, a reflective layer electrically contactingthe ohmic contact layer, a first material barrier layer electricallycontacting the reflective layer, a current carrying layer electricallycontacting the first material barrier layer, and a second materialbarrier layer electrically contacting the current carrying layer; anN-electrode metal contained by the N-ohmic contact-reflective material,a dielectric material which insulates the P-type layer and the activeregion from the N-ohmic contact-reflective material; and a P-electrodemetal in electrical contact with the P-type layer of each of the mesas.2. The LED device of claim 1, wherein the N-ohmic contact-reflectivematerial is in direct contact with the N-type layer.
 3. The LED deviceof claim 1, wherein the N-type layer comprises n-GaN and: the ohmiccontact layer comprises: aluminum (Al), titanium (Ti), or aluminum-dopedzinc oxide (AZO), the reflective layer comprises silver (Ag) or gold(Au); the first and second material barrier layers each independentlycomprise: titanium (Ti), chromium (Cr), platinum (Pt), cobalt (Co),palladium (Pd), or tungsten (W), and the current carrying layercomprises: copper (Cu), gold (Au), or aluminum (Al).
 4. The LED deviceof claim 1, wherein: the ohmic contact layer comprises a thickness in arange of greater than or equal to 5 Å to less than or equal to 200 Å,the reflective layer comprises a thickness of greater than or equal to1000 Å, the first and second material barrier layers each independentlycomprise a thickness of greater than or equal to 1000 Å, and the currentcarrying layer comprises a thickness of greater than or equal to 5000 Å.5. The LED device of claim 1, wherein the N-ohmic contact-reflectivematerial further comprises a first material migration suppression layerelectrically contacting the reflective layer and the first materialbarrier layer; and a second material migration suppression layerelectrically contacting the current carrying layer and the secondmaterial barrier layer.
 6. The LED device of claim 5, wherein the firstand second material migration suppression layers each independentlycomprise nickel (Ni) or palladium (Pd), and/or independently comprise athickness in a range of greater than or equal to 50 Å to less than orequal to 1000 Å.
 7. The LED device of claim 1 further comprising aP-ohmic contact-reflective material containing the P-electrode metal,wherein the P-ohmic contact-reflective material has the same structureas the N-ohmic contact-reflective material.
 8. The LED device of claim1, wherein each of the mesas has at least one characteristic dimensionof less than 100 micrometers, the character dimension being selectedfrom the group consisting of: height, width, and depth.
 9. The LEDdevice of claim 1, wherein the semiconductor layers are epitaxialsemiconductor layers having an overall thickness in a range of from 2 μmto 10 μm.
 10. The LED device of claim 1, wherein each of the mesasincludes sidewalls of the semiconductor layers defining an angle in arange of from 60 degrees to 90 degrees from a horizontal plane that isparallel with the N-type layer and the P-type layer.
 11. The LED deviceof claim 1, wherein the plurality of mesas are integral to a monolithicdie.
 12. The LED device of claim 1, wherein the semiconductor layers areon a substrate.
 13. A method of manufacturing a light emitting diode(LED) device comprising: preparing a plurality of mesas and trenches,each of the mesas comprising semiconductor layers, the semiconductorlayers including an N-type layer, an active region, and a P-type layer,and each mesa having a top surface and at least one mesa sidewall, andthe trenches defined by respective mesa sidewalls and each having abottom surface; exposing the N-type layer; preparing an N-ohmiccontact-reflective material electrically contacting the N-type layer ofeach of the mesas by: depositing an ohmic contact layer electricallycontacting the N-type layer and having a work function value that isless than or equal to a work function value of the N-type layer,depositing a reflective layer electrically contacting the ohmic contactlayer, depositing a first material barrier layer electrically contactingthe reflective layer, depositing a current carrying layer electricallycontacting the first material barrier layer, and depositing a secondmaterial barrier layer electrically contacting the current carryinglayer; depositing and patterning an N-electrode metal contained by theN-ohmic contact-reflective material and a P-electrode metal inelectrical contact with the P-type layer of each of the mesas; anddepositing and patterning a dielectric material which insulates theP-type layer and the active region from the N-ohmic contact-reflectivematerial.
 14. The method of claim 13 comprising depositing the N-ohmiccontact-reflective material directly on the N-type layer.
 15. The methodof claim 13, wherein the N-type layer comprises n-GaN, and the ohmiccontact layer comprises: aluminum (Al), titanium (Ti), or aluminum-dopedzinc oxide (AZO); the reflective layer comprises silver (Ag) or gold(Au); the first and second material barrier layers each independentlycomprise: titanium (Ti), chromium (Cr), platinum (Pt), cobalt (Co),palladium (Pd), or tungsten (W); and the current carrying layercomprises: copper (Cu), gold (Au), or aluminum (Al).
 16. The method ofclaim 13, wherein: the ohmic contact layer comprises a thickness in arange of greater than or equal to 5 Å to less than or equal to 200 Å,the reflective layer comprises a thickness of greater than or equal to1000 Å, the first and second material barrier layers each independentlycomprise a thickness of greater than or equal to 1000 Å, and the currentcarrying layer comprises a thickness of greater than or equal to 5000 Å.17. The method of claim 13 further comprising: depositing a firstmaterial migration suppression layer electrically contacting thereflective layer and the first material barrier layer; and/or a secondmaterial migration suppression layer electrically contacting the currentcarrying layer and the second material barrier layer.
 18. The method ofclaim 17, wherein the first and second material migration suppressionlayers each independently comprise nickel (Ni) or palladium (Pd), and/orindependently comprise a thickness in a range of greater than or equalto 50 Å to less than or equal to 1000 Å.
 19. The method of claim 13,wherein a P-bonding material is also prepared contacting the P-typelayer by depositing the ohmic contact layer electrically contacting theP-type layer, depositing the reflective layer electrically contactingthe ohmic contact layer, depositing the first N-bonding material barrierlayer electrically contacting the reflective layer, depositing thecurrent carrying layer electrically contacting the first materialbarrier layer.
 20. The method of claim 13, wherein each of the mesas hasat least one characteristic dimension of less than 100 micrometers, thecharacter dimension being selected from the group consisting of: height,width, and depth.